Vehicle cooling systems provide a vehicle engine with coolant to cool the engine. Coolant may be circulated through the cooling system by a water pump. The coolant may flow from the water pump to the engine, and as the coolant passes through the engine, it absorbs heat from the engine. Heated coolant then flows to a radiator in the cooling system to be cooled before returning again to the engine. Traditional radiators may comprise a fan which blows air through the radiator and cools the coolant passing through the radiator. Specifically, the radiator may include a plurality of tubes for flowing coolant therethrough and heat conductive fins to increase heat transfer from the coolant in the tubes to ambient air. However, the effectiveness of the radiator in cooling the coolant may be decreased under certain operating conditions, such as when the ambient air temperature is above a threshold. Moreover, if the temperature of the coolant reaches the boiling point of the coolant, coolant may be vaporized and lost from the cooling system and the effectiveness of the coolant in cooling the engine may be decreased, which may, in turn, lead to engine degradation.
Previous attempts to address the vaporization of coolant include utilizing phase change material (PCM) to absorb excess heat from the coolant. PCM is used as a heat absorber because of its high latent heat of fusion. When a solid material reaches its melting point, energy can be added to the material, without increasing the temperature of the material. This is because energy is required to change the phase of a material from solid to liquid. The amount of energy required to melt a material without changing its temperature may be referred to as its latent heat of fusion. Because of PCM's large latent heat of fusion, it is able to absorb a significant amount of heat while maintaining its temperature. Thus, incorporating PCM into a cooling system may increase the efficiency of the cooling system.
One example approach to employ the use of PCM in a cooling system to reduce excessive coolant temperatures is shown in U.S. Pat. No. 7,735,461, which provides an auxiliary line downstream of a radiator, the auxiliary line containing PCM capsules. Coolant may be directed through the auxiliary line containing the PCM capsules if the coolant temperature increases above a threshold, where the threshold may be the melting temperature of the PCM. Because the coolant is at a higher temperature than the PCM, the PCM may naturally draw heat from the coolant, raising the temperature of the PCM. However, when the PCM reaches its melting point, because of the PCM's high latent heat of fusion, it may continue to draw heat from the coolant without its own temperature being raised. Therefore, the PCM provides increased cooling over other materials with lower latent heats of fusion. As such, the system provided in U.S. Pat. No. 7,735,461, may divert coolant flow through the auxiliary line containing PCM, to increase coolant cooling efficiency at high coolant temperatures.
However, the inventors herein have recognized potential issues with such systems. Adding an auxiliary line containing PCM to a cooling system increases the amount of piping and number of valves in the cooling system. Thus, the cost, packaging size, and complexity of such cooling systems may be increased. Further, due to the additional plumbing required by such systems, the chances of leakages, and malfunctions in such systems are increased.
Thus, the inventors herein have provided a system and methods for addressing the issues described above. In one example, the issues described above may be addressed by a method comprising, adjusting a radiator control valve into a first position to flow coolant only through a first zone of a radiator containing phase change material (PCM) and not through a second zone of the radiator not containing phase change material, and adjusting the radiator control valve into a second position to flow coolant only through the second zone of the radiator and not the first zone. In this way, the efficiency of a radiator may be increased, while both its size and power consumption may be decreased. As such, the fuel efficiency of an engine may be increased.
As one example, the first and second zones may comprise hollow tubes for flowing coolant therethrough. The second zone may comprise heat conductive fins for increasing heat dissipation from coolant flowing through the second zone. However, the tubes in the first zone may instead be encased in PCM. As such, the thermal absorption efficiency of the first zone may be greater than the second zone at coolant temperatures above the melting temperature of the PCM. Thus, for coolant temperature above the threshold, the radiator control valve may be adjusted to a first position to flow coolant through the first zone of the radiator. For coolant temperatures below the threshold, the radiator control valve may be adjusted to a second position to flow coolant through the second zone of the radiator. Thus, by flowing coolant through the first zone of the radiator containing PCM when coolant temperatures exceed a threshold, the coolant may be cooled more effectively, and thus, the amount of coolant lost to vaporization may be reduced. Furthermore, by incorporating the PCM within the radiator and regulating coolant flow within the radiator with the control valve, the overall compactness and efficiency of the cooling system may be increased, while the cost and size may be reduced.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.